This invention relates to the measuring of the gas and/or water content of oil, and in particular to a method and apparatus for measuring the proportions of gas, water and oil in a crude oil flowing mixture.
The production of oil through wells and production pipelines is usually accompanied by the production of some associated gas or water. The measurement of the volume fractions of such components in the flowing system is of importance in any oil production system, but particularly in the case of offshore production where several wells may be connected to a subsea manifold with one riser or pipeline to the surface. A knowledge of the oil, water and gas components in the pipeline from each well would provide information needed for better control of a production system and the producing reservoir.
Several techniques exist for measuring one or more of these components. For example, capacitance or microwave techniques are used to measure water content in a flowing pipeline; gamma-ray or neutron techniques can be used to measure the void or gas fraction.
Another method involves the use of an oil/water separator for measuring the volume of water in crude oil. However, such a method measures the quantity of water by batch only. In crude oil, water and oil are often emulsified, in which case separation is incomplete which results in erroneous measurements. Moreover, the quantity of gas in the oil must be measured separately, and since regulatory bodies usually require individual well flow measurements on a frequent basis, a separate test separator is needed for this purpose. Since the oil/water separator is large, and occupies precious space on a production or drilling platform, there exists a need for a reliable method of measuring the proportions of gas and water in flowing crude oil from an individual well or combined well flow. The object of the present invention is to meet such a need.